China eyes birds as H7N9 source as human cases rise to 33

Apr 10, 2013 (CIDRAP News) – Five more H7N9 influenza infections have been confirmed in eastern China, all in older adults, while suspicions grow that wild birds may be the source and that the disease might be spreading to people through poultry environments.

Newly reported cases include two women from Shanghai, two men from Jiangsu province, and a man from Zhejiang province, according to separate reports today from Hong Kong's Centre for Health Protection (CHP). The illnesses boost China's number of infections with the new virus to 33, with the number of deaths holding steady at 9.

The Shanghai women are ages 76 and 81, and both are in stable condition. Of the Jiangsu men, a 70-year-old is in critical condition and a 74-year-old is in serious condition. The man from Zhejiang is 65 years old and is in stable condition.

Illness-onset dates were available for all but the Zhejiang man and range from Mar 29 to Apr 4. Most of the cases so far have been reported in middle-aged and older adults.

The World Health Organization (WHO) issued an update today on four cases that China first announced yesterday and emphasized that so far no evidence of human-to-human spread has been detected. It said Chinese officials are monitoring more than 600 close contacts and that an investigation is under way into a patient who got sick after contact with an earlier confirmed case in Jiangsu province.

In its Twitter feed today, the WHO said the behavior of the virus is more important than the exact case count. So far almost all confirmed cases have involved animal-to-human or environment-to-human transmission, such as in a farmyard or market setting.

"We will be watching for signs of human-to-human transmission and new cases in other geographical areas," the WHO said.

On the animal front, China's agriculture ministry has detected the virus at five more live-bird markets in three different eastern provinces, all of which have reported human cases, according to a report today from the World Organization for Animal Health (OIE). Three markets are in Jiangsu, one is in Anhui, and one is in Zhejiang.

The report didn't specify what type of birds tested positive but said the virus was detected in samples from 14 asymptomatic birds. Authorities will cull the birds to curb the spread of the virus.

Earlier notifications of bird and poultry H7N9 findings involved only markets in Shanghai, according to previous OIE reports. The disease has been difficult to track in poultry, because the virus is low pathogenic in birds, and they don't show signs of disease.

Meanwhile, researchers from a Chinese biology lab said today that the H7N9 virus is a reassortment of viruses from wild birds in East Asia and chickens from east China, Xinhua, China's state news agency, reported today.

Researchers from the Chinese Academy of Sciences Key Laboratory of Pathogenic Microbiology and Immunology said their analysis found no links to pigs, which would exclude them as intermediate hosts, according to the report.

Scientists surmised that genetic reassortment probably occurred in east China's Yangtze River Delta area, which encompasses Shanghai, Zhejiang, and Jiangsu. They said a virus carried by wild birds from South Korea and nearby regions mingled with ducks and chickens in the delta area during migration.

The group reported that the H7 and N9 gene segments resemble those seen in East Asian wild birds and that the other six genes have links to chickens in Shanghai, Zhejiang, and Jiangsu, Xinhua reported.

China's wildlife conservation centers have bolstered their bird monitoring efforts to see if birds currently migrating from the south to the north are carrying the virus, amid fears that it could spread to the country's northern provinces, according to a separate report from Xinhua today. About 10 centers are monitoring the virus, including one in north China's Hebei province.

The European Centre for Disease Prevention and Control (ECDC) today underscored its advice that travelers avoid live-poultry markets, especially in light of the recent H7N9 developments.

In an epidemiologic update, the ECDC said that there is no need for travel restrictions, but it said Europeans working in or visiting China and other Asian countries should avoid live markets and direct contact with birds, untreated bird feathers, and other animal and bird waste.

The ECDC urged travelers to observe good hand hygiene, consisting of regular hand washing and the use of alcohol-based rubs. "This is the same advice that ECDC has had in place since 2006," the group said.